Part of the subtype.
Demodand wrote:
Faith-Stealing Strike (Su) When a demodand’s natural attack or melee weapon damages a creature capable of casting divine spells, that creature must make a Will saving throw or be unable to cast any divine spells for 1 round. Once a creature makes this save, it is immune to further faith-stealing strikes from that particular demodand for 24 hours. The save DC is Charisma-based.
You can find it in the back of the book under subtypes. Behemoth and Kaiju have the same problem.
